title: Expression of three immunoglobulin isotypes by individual B cells during development: implications for heavy chain switching.
abstract: Previous studies in mice and humans have shown that the first IgA+ and IgG+ B cells appearing during ontogeny also bear IgM on the surface. The acquisition of IgD seems to occur at a later stage in differentiation. In this study we have combined autoradiography with two-color immunofluorescence to directly detect human B cells expressing three surface isotypes. We report that the vast majority of IgA+ cells in the neonate also bear IgM and IgD; the same holds true for IgG+ cells. This phenotype is peculiar of newborns, while in the adult the majority of IgA+ and IgG+ cells are single. We discuss the genetic implications of such a finding for heavy chain switching.
mesh_terms: D000328:Adult; D000367:Age Factors; D001402:B-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation; D005260:Female; D005312:Fetal Blood / Q000276:immunology; D005786:Gene Expression Regulation; D005802:Genes, MHC Class II; D006801:Humans; D007126:Immunoglobulin Allotypes; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007231:Infant, Newborn; D011247:Pregnancy
chemical_list: D007126:Immunoglobulin Allotypes; D007143:Immunoglobulin Heavy Chains